Systems for weighing a pulled object

Abstract

Pulling systems are disclosed for measuring the weight of an object coupled to a first end of a cable. The cable is routed over a pulley suspended from a load cell. The force exerted by the cable on the pulley is used to calculate the weight of the object. The second end of the cable is coupled to a drum which when rotated pulls the object by wrapping the cable around the drum. An arm is coupled to the pulley at one end and to a frame at another end. A path travelled by the cable between the pulley and the drum is substantially parallel to a longitudinal axis of the arm. Horizontal force components are transmitted by the arm to the frame and do not affect a force component measured by the load cell, thus increasing the accuracy of the calculated weight of the object.

What is claimed is: 
     
       1. An apparatus for measuring the weight of an object while pulling the object upward, the apparatus comprising:
 a frame having a vertical axis and a horizontal axis, the vertical axis parallel to an axis along which the object is pulled, the horizontal axis being orthogonal to the vertical axis; 
 a cable connected to the object; 
 a first cylinder rotatably mounted on the frame, at least a portion of the cable engaging a surface of the first cylinder; 
 a second cylinder rotatably mounted on the frame, at least a portion of the cable engaging a surface of the second cylinder, the cable travelling along a cable path between the first cylinder and the second cylinder; 
 an arm having a first end and a second end, the first end coupled to at least one of the frame and the second cylinder, the second end coupled to the first cylinder, the arm having a longitudinal axis substantially parallel to the cable path and connecting the first and second ends, wherein the arm substantially restrains the first cylinder from movement parallel to the horizontal axis; 
 a force measurement device for measuring the weight of the object, the force measurement device coupled to the first cylinder; and 
 an actuator operable to raise and lower the first cylinder such that the cable remains stationary with respect to the first cylinder while the object is pulled upward. 
 
     
     
       2. The apparatus of  claim 1  wherein the first cylinder is rotatable about a center axis and the second cylinder is rotatable about a center axis, and wherein the second end of the arm is coupled to the center axis of the first cylinder. 
     
     
       3. The apparatus of  claim 1  wherein the arm is resistant to elongation in a direction substantially parallel to the longitudinal axis of the arm. 
     
     
       4. The apparatus of  claim 1  wherein the first cylinder includes a first pulley and the second cylinder includes a second pulley. 
     
     
       5. The apparatus of  claim 1  wherein the second cylinder is a spool, the second end of the cable coupled to at least a portion of the spool and the cable coiled around the spool. 
     
     
       6. The apparatus of  claim 1  further comprising a bushing at least partially surrounding a portion of the cable, the bushing configured to control the position of the cable with respect to the frame. 
     
     
       7. The apparatus of  claim 6  wherein the bushing is movable between a first position in which the bushing is in contact with the cable and a second position in which the bushing is not in contact with the cable. 
     
     
       8. The apparatus of  claim 4  further comprising a spool, the second end of the cable coupled to at least a portion of the spool and the cable coiled around the spool. 
     
     
       9. The apparatus of  claim 1  wherein the object is a growing silicon ingot and wherein the weight of the ingot increases as the ingot grows. 
     
     
       10. The apparatus of  claim 1  wherein the frame is rotatable about its vertical axis. 
     
     
       11. The apparatus of  claim 1  further comprising a puller for pulling the object upward. 
     
     
       12. A pulling system for measuring an amount of force required to pull an object across a surface, the pulling system comprising:
 a frame having a first axis and a second axis, the first axis parallel to an axis along which the object is pulled, the second axis being orthogonal to the first axis; 
 a cable coupled to the object; 
 a first cylinder rotatably coupled to the frame, at least a portion of the cable engaging a surface of the first cylinder; 
 a second cylinder rotatably coupled to the frame, at least a portion of the cable engaging a surface of the second cylinder, the cable travelling along a cable path between the first cylinder and the second cylinder; 
 an arm having a first end and a second end, the first end coupled to the frame and the second end coupled to the first cylinder, the arm having a longitudinal axis substantially parallel to the cable path and connecting the first and second ends; and 
 a force measurement device for measuring the amount of force required to pull the object across the surface, the force measurement device coupled to the first cylinder. 
 
     
     
       13. The pulling system of  claim 12  wherein the first cylinder is rotatable about a center axis and the second cylinder is rotatable about a center axis and the second end of the arm is coupled to the center axis of the first cylinder. 
     
     
       14. The pulling system of  claim 12  wherein the second cylinder is a spool, the second end of the cable coupled to at least a portion of the spool and at least a portion of the cable coiled around the spool. 
     
     
       15. The pulling system of  claim 12  wherein the first axis is other than vertical and the second axis is other than horizontal. 
     
     
       16. The pulling system of  claim 12  wherein the arm is substantially rigid and resistant to elongation in a direction substantially parallel to the longitudinal axis of the arm. 
     
     
       17. The pulling system of  claim 12  further comprising a spool, the second end of the cable coupled to at least a portion of the spool and the cable coiled around the spool. 
     
     
       18. A crystal growing apparatus for growing monocrystalline silicon ingots, the crystal growing apparatus comprising:
 a crucible for containing molten silicon; 
 a puller for pulling a growing ingot upward from the molten silicon, the puller including: 
 a frame having a vertical axis and a horizontal axis, the vertical axis parallel to an axis along which the growing ingot is pulled, the horizontal axis being orthogonal to the vertical axis; 
 a cable coupled to the growing ingot; 
 a first cylinder rotatably coupled to the frame, at least a portion of the cable engaging an outer circumferential surface of the first cylinder, the first cylinder suspended from a force measurement device; 
 a second cylinder rotatably coupled to the frame, at least a portion of the cable engaging an outer circumferential surface of the second cylinder; 
 an arm having a first end and a second end, the first end coupled to the frame and the second end coupled to the first cylinder, the arm having a longitudinal axis substantially parallel to the horizontal axis of the frame; and 
 an actuator operable to raise and lower the first cylinder such that the cable remains stationary with respect to the first cylinder while the object is pulled upward. 
 
     
     
       19. The crystal growing apparatus of  claim 18  wherein the first cylinder is rotatable about a center axis and the second cylinder is rotatable about a center axis and wherein the second end of the arm is coupled to the center axis of the first cylinder. 
     
     
       20. The crystal growing apparatus of  claim 18  wherein the cable travels along a cable path between the surface of the first cylinder and the surface of the second cylinder, and wherein the cable path is substantially parallel to the longitudinal axis of the arm. 
     
     
       21. The crystal growing apparatus of  claim 18  wherein the second cylinder is a spool, the second end of the cable coupled to at least a portion of the spool and the cable coiled around the spool. 
     
     
       22. The crystal growing apparatus of  claim 18  wherein the arm is rigid and substantially restrains the first cylinder from movement parallel to the horizontal axis of the frame. 
     
     
       23. The crystal growing apparatus of  claim 18  wherein the frame is rotatable about its vertical axis. 
     
     
       24. The crystal growing apparatus of  claim 18  wherein the frame is disposed in a housing.